There is a continuing need for lighting apparatus which is low-cost and energy efficient. LEDs (light-emitting diodes) provide light sources which are energy efficient; and advances in LED technology are providing even greater efficiencies over time.
Some of the newer applications for LED-based lighting systems are roadway and parking lot lighting in which there are desired performance and light-distribution characteristics. More specifically, it is desirable that certain regions generally beneath a light fixture be illuminated, while certain neighboring regions are essentially non-illuminated. Along roadways and in parking lots, there is a need to be able to direct light in a particular preferential lateral direction (e.g., to illuminate a roadway) while avoiding so-called “trespass light” in an opposite lateral direction (a non-preferential lateral direction), e.g., toward roadside houses.
The importance of avoiding trespass light (or the like) is such that in some cases sacrifices are made in lighting efficiency, by virtue of allowing absorption of light by shielding members. It would be highly desirable to provide a high-efficiency LED lighting system for roadways, parking lots and the like that avoids trespass light without significant efficiency losses.
It would be further desirable to provide a lighting fixture that maintains the desired light-directing characteristics and efficiency of operation at a substantially constant level throughout the fixture life. Such continued combination of advantages can be difficult to achieve because of susceptibility of light-managing components to damage, degradation and wear over a period of time.